As an ideal physical platform for accessing multiple services such as voice, data and video through a single platform, the Passive Optical Network (PON) has become one of the leading competitors in the filed of optical access technology due to its easy maintenance, high bandwidth and low costs. The PON is a Point-to-Multipoint (P2MP) optical access technique. A PON consists of an Optical Line Terminal (OLT), an Optical Network Unit (ONU) and an Optical Distribution Network (ODN). The PON takes advantage of the splitter/coupler in the ODN, therefore the PON no longer needs elements with amplifying and relaying functions. Due to its P2MP topology, the PON has to use a P2MP multiple access protocol so that the OLT and the optical fiber may be shared by the ONUs. According to carried contents, PONs may be classified into many categories, among which the Ethernet Passive Optical Network (EPON) is a widely used one with good performances.
In PON systems, downstream refers to the direction in which data is transmitted from the OLT to the ONU, and upstream refers to the direction from the ONU to the OLT. A widely used transmission method in PON is to broadcast using Time Division Multiplexing (TDM) for downstream and to access using Time Division Multiple Access (TDMA) for upstream. Upstream transmission in PON systems is based on burst mode, and data from multiple ONUs is transmitted to an OLT. The OLT has to delimit data from respective ONUs in burst mode, so that the received data from respective ONUs may be distinguished. In the prior art, the OLT authorizes an transmitting time slot for each ONU, based on which the MAC layer of the OLT knows the starting time and ending time of burst data from each ONU. Therefore, by adding an interface between the MAC layer and the physical layer and using a Management Data Input/Output (MDIO) register, the MAC layer of the OLT may inform the physical layer of the OLT of when data received from an ONU ends. Upon knowing the ending point of the data, the physical layer of the OLT starts a burst delimiter search, and matches on data from the next ONU. If the matching succeeds, the OLT knows the starting point of the ONU data, and begins to receive the data from the ONU. However, in the prior art, the MDIO register has to communicate with an upper layer application of the OLT. Therefore, an interface between the MDIO register and the upper layer of the OLT has to be added, which breaks down functional independence of the MDIO register and changes the interface between the MAC layer and the physical layer. Such a solution is complicated.